Let weapons auto-target allies

For things like healing beams or bursty reimplementation of nanolathe. Perhaps the existing sets of avoidX and collideX could be extended with targetX so that e.g. features could be targeted too (think zk puppy which could throw itself at reclaim).

Don't be fooled by the short description, this is a very large task.

No files, tests, or entry points are named. Start by locating the existing avoidX and collideX targeting or collision systems and determine how weapons select allies and features. Done should include support for ally auto-targeting for healing beams or nanolathe-like effects, with the broader targeting behavior defined.

Written by the indexing model from the issue text.